Obscurins, cytoskeletal proteins discovered about a decade ago, are encoded by the single OBSCN gene and have been primarily studied in vertebrate striated muscles. The giant (~720-900 kDa) obscurin isoforms intimately surround sarcomeres at M-bands and Z-disks, where obscurins participate in their assembly, stability, and integration with other sarcomeric elements. The PI and her primary mentor (Dr. Kontrogianni- Konstantopoulos) are at the forefront of characterizing this novel family of proteins. Recently, the PI has identified a novel obscurin isoform (obscD), resulting from complex differential splicing at the 3' end of the gene that preferentially concentrates at the intercalated disc (ID) of cardiomyocytes. The ID is a unique membrane microdomain that mediates mechanical and electrical coupling between neighboring cells, allowing the synchronous beating of the heart. Importantly, mutations and disruptions of ID proteins interrupt regular heart function, consequently leading to heart disease. Consistent with its ID localization,biochemical assays indicate that obscD exists in a complex with other proteins of the ID proteome. Furthermore, preliminary proteomic analysis has indicated that obscD is regulated via phosphorylation, and its phosphorylation state is altered in the dystrophic disease model. This project aims to elucidate the function that obscD plays at the ID and determine the role of obscD's phosphorylation in physiology and pathophysiology. The PI has assembled an accomplished individualized mentoring committee who will provide the necessary training and support to accomplish the proposed research, as well as facilitate the growth of the PI. The PI will remain at UM SOM, working under the guidance of Drs. Kontrogianni-Konstantopoulos, Rogers, and Stanley. Additionally, the PI will also benefit from the enrichment of Dr. Sellers, at nearby NIH. Through this mentoring team and the collaborations set up by the PI, she will have access to both routine and state-of-the-art equipment and reagents necessary to successfully and efficiently complete the proposed research. In addition, the PI will have excellent resources for career development at the UM SOM and NIH campuses. The proposed research and career development plan will enable the PI to investigate the phosphorylation of obscD and elucidate its in vivo physiological and pathophysiological function at the ID. Furthermore, they will facilitate her development as a diversified independent muscle biology investigator who integrates traditional biochemical and molecular biology techniques with whole tissue translational approaches.